Excited-State Planarization as Free Barrierless Motion in a π-Conjugated Terpyridine
-
Siebert, Ronald; Winter, Andreas; Schubert, Ulrich S.; Dietzek, Benjamin; J\", ; urgen Popp,
- Abstract:
- We present femtosecond time-resolved transient absorption data and results from nanosecond time-resolved
emission studies for an extended terpyridine system (4′-(4-((2,5-bis(octyloxy)-4-styrylphenyl)ethynyl)phenyl)-
2,2′:6′,2′′-terpyridine). By variation of selected solvent properties, that is, solvent viscosity, polarity, and
temperature, we can dissect kinetic components, which are due to photoinduced molecular structure
rearrangements of the terpyridine system. This real-time observation allows us to quantify the influence of
the solvent viscosity on the structural rearrangements, which becomes slowed from 20 to 100 ps when changing
the solvent from methanol to n-butanol. By adding temperature-dependent time-resolved emission experiments
to the study, we show that the relaxed S1 state partially decays via a nonradiative channel which can be
assigned to an intersystem crossing to a lower lying T1 state. The data presented in this paper directly visualize
excited-state planarization of the terpyridine sphere in real time. Such motion of the terpyridine with respect
to the adjacent conjugated rest leads to a highly conjugated chromophore and is causative for the observed
photophysical features of the ligands and their transition metal complexes.
- Year:
- 2010
- Type of Publication:
- Article
- Journal:
- Journal of Physical Chemistry C
- Volume:
- 114
- Pages:
- 6841 - 6848